This invention relates to novel poly(imidesiloxane) block copolymers and a process for their preparation. More particularly, the invention concerns novel thermoplastic, injection moldable poly(imidesiloxane) block copolymers.
Heretofore, poly(imide-siloxane) copolymers have been prepared by reacting aromatic bis(dicarbonyl) compounds with amine-terminated polydiorganosiloxanes. These procedures have resulted in polymers in which the siloxane and polyimide segments are bonded together through imide linkages. For example, in U.S. Pat. Nos. 3,325,450 and 3,740,305, Holub discloses polymers prepared by reacting an aromatic dianhydride with an organic diamine and a diaminosiloxane in an organic solvent Similarly, U.S. Pat. No. 3,833,546 (Takekoshi et al.) and U.S. Pat. No. 3,847,867 (Heath et al.) disclose processes for making poly(imide-siloxane) copolymers which involve reacting an aromatic bis(ether anhydride) or an aromatic bis(ether dicarboxylic acid) with an aminoalkylene-terminated polydiorganosiloxane.
In U.S. Pat. No. 4,051,163, Berger discloses a process involving reacting an aromatic dianhydride with an organic diamine and an aminoalkylene-terminated polydiorganosiloxane in an organic solvent to form an amideacid block copolymer. The amideacid copolymer may be used as a coating material, which is converted to a poly(imide-siloxane) block copolymer in situ by curing at elevated temperatures. Berger further discloses, in U.S. Pat. No. 4,011,279, a process for making poly(imidesiloxane) copolymers which comprises reacting an aromatic dianhydride with an organic diamine to form an anhydride-terminated polyimide prepolymer, then reacting the polyimide prepolymer with an amine-terminated polydiorganosiloxane.
There is increasing interest in poly(imidesiloxane) block copolymers, particularly for use as modifiers for other polymer systems. Moreover, a need exists for more efficient and economical processes for preparing these valuable polymers.